DE102004046744B4 - Process for transferring powders and powder coatings to substrates and use for the production of printed circuit boards and solar cells - Google Patents

Abstract

method for thorough mixing and gentle transport and transmission of powders on substrates, wherein the powder particles by Friction in the presence of magnetic particles are charged then by means of a fluidized bed and optionally one or more mixing rollers transported and subsequently by means of an electric field between a brushing drum and a substrate roll on which the substrate is located, transferred to the substrate and be applied, characterized in that the mixing and the transport of the powder particles and the magnetic particles be carried out by means of a fluidized bed, wherein the powder continuously deposited on the substrate and at the same time of to eat supplied will, while the magnetic particles (carriers) remain in the system.

Description

The Invention relates to a method according to the preamble of claim 1 for gentle transmission of powders on substrates and in particular for transfer to conductive substrates such as metal foils, conductive polymers, metallic coated polymers, coated glasses, such as. ITO (indium tin oxide) glass, for example in the production of printed circuit boards and solar cells (claim 12) using the fluidized bed or fluidized bed process and magnetic carrier particles.

The production of differently thick layers of lacquer plays an outstanding role in the production of printed circuit boards. Thus, for example, copper foils are coated with solvent-dissolved epoxy resin formulations and the solvent is subsequently evaporated. The films thus obtained are then pressed on already pre-structured so-called inner layers in a vacuum ( US 5,718,039 A . US Pat. No. 6,187,416 B1 . EP 1 108 532 A1 ). Another example is applying the solder mask to the finished circuit board. The corresponding formulations also include solvent or water, which must be removed thermally ( EP 0 323 563 A1 ).

The Disadvantages of this on solvents based methods are the high energy consumption during evaporation the solvent, endangering the environment, complex work hygiene measures, flammability of solvents, costly disposal and consequently considerable additional Costs.

A Alternatives to this are provided by methods that use formulations as Powder can be used, process. In the literature are described spraying powder, Powder cloud, electromagnetic brush (Pieter Gillis de Lange, Powder Coatings-Chemistry and Technology, 2nd edition, Vincentz Network, Hannover 2004). The first two options are industrial Application in the paint processing industry. An application in the PCB area is contrary to the uneven layer thickness, which can be achieved with these methods.

at the use of the so-called electromagnetic brush Powder coatings or powder paint particles using magnetic brushes on conductive or the charge laxative Transfer substrates. These methods are based on the same principle, which also applies to laser printers and copy machines application finds. The powder to be applied is in a tank or container with carrier particles or carrier particles, so-called carriers, mixed. These consist of a magnetic Core, with a plastic coating is provided.

By mechanical mixing by means of several rollers, the powder charges electrostatically which makes it stick to the carriers. Transport the mixing rollers continuously the powder with the carrier to the so-called Bürstrolle, which is provided with magnets inside. The magnetic carrier particles with the powder adhering to them now in turn remain on the roll hang. Will now between the Bürstrolle and the substrate drum applied a corresponding voltage, so the powder particles jump onto the substrate (e.g., a metal foil), however, the carrier particles remain in the system.

In U 4 359 516, powders are charged in the presence of magnetic particles and subsequently transferred and applied to the substrate by applying an electric field between a brushing drum and a substrate roller. In US 5,407,743 A discloses a process for coating substrates with zinc oxide-containing coatings by applying and oxidizing a zinc oxide precursor. A method of coating solar cells with a matrix layer of electrically nonconductive fibers is known in US 5,672,214 described. In DE 698 07 934 T2 A process for applying powder coating compositions by incorporating the substrate in a fluidized bed and transferring the powder using electrical charging will be described. In US 4,169,187 discloses a coating process with epoxy resins followed by curing with a crosslinking agent.

Short description of Characters:

1 describes schematically a coating system with mixing drums. In the container ( 10 ) Carrier and powder are mixed. As a result, the powder charges and adheres to the oppositely charged carriers. The transport takes place through the mixing rollers ( 3 ) to the brushing drum ( 1 ). The mixing rollers or mixing drums ( 3 ) may have magnets inside. Optionally, they have wings or paddles on the outside. They serve to mix the carrier and the powder or powder coating. The mixing rollers ( 3 ) take over the transport of the particles to the brushing drum ( 1 ). The brushing drum ( 1 ) has magnets in its interior. By applying a voltage between the brushing drum ( 1 ) and a substrate drum ( 2 ) are the ge powder particles repelled and land on the grounded substrate, which is located on the substrate drum ( 2 ) is located. The substrate (eg a copper foil) is separated from a roll ( 6 ) unrolled. The substrate must be able to remove the charge.

In 1 further shown are a heat source ( 7 ), which serves to melt the powder coating or to sinter the powder. ( 4 ) means a sheet for returning the carrier into the container. ( 8th Finally, designates a roll for winding the coated substrate.

2 shows the modification according to the invention with fluidized bed or fluidized bed: The in 1 shown mixing rollers ( 3 ) are replaced by a fluidized bed (in 2 represented by dots). By blowing air into the mixture of carrier and powder or powder coating creates the fluidized bed, which thus ensures a thorough mixing and thus for the mutual charging of carrier and powder. In addition, the transport to the brushing drum is accomplished.

On this way you can continuously uniform thickness Layers are applied to a substrate. The Schichtdickenverfeilung is while ± 15%, preferred ± 10% and most preferably ± 5%.

With the method according to the invention can Layer thicknesses in the range of 5 microns up to 100 μm to be obtained.

• a) der Antriebsmotor muss eine hohe Leistung haben,
• b) wodurch die Carrier einer hohen mechanischen Beanspruchung ausgesetzt sind,
• c) welche die dünne Beschichtung der Carrier rasch zerstört, was zu einer Verschlechterung der Aufladung und demzufolge zu einer Verringerung der Lebensdauer führt.
• d) Das Anfahren der Maschine ist schwierig, häufig ist sie blockiert, da die schwere Mischung die Rotation der Walzen verhindert.

In this case, the powder to be applied is continuously deposited on the substrate and at the same time fed from the outside. The carriers remain in the system. The mixing takes place according to the prior art mechanically by rolling. This mixing also serves to charge the friction of the powders, which subsequently adhere to the carriers. The transfer to the first roll is carried out by paddle wheels or magnetic rollers, which dip into the mixture. The mixture is very compact, with the following consequences:

• a) the drive motor must have a high power,
• b) whereby the carriers are exposed to high mechanical stress,
• c) which rapidly destroys the thin coating of the carrier, which leads to a deterioration of the charge and consequently to a reduction in the life.
• d) Starting the machine is difficult, it is often blocked because the heavy mixture prevents the rollers from rotating.

One Another problem is the lifetime of the carrier particles. by virtue of the mechanical stress caused by the mixer rollers and because of the between the brushing drum and the substrate drum voltage applied wear the Carrier over time, so they need to be replaced. This causes additional Costs, on the one hand the acquisition of the carrier itself, but also because the machine has to be turned off and thereby the Machine running time significantly reduced.

The invention is therefore based on the object, a method for the careful transport of powder mixtures in such coating systems and thus for the transmission of powders and powder coatings on substrates, in particular conductive substrates such as metal foils to provide. On the basis of known methods (cf., eg US 4,359,516 and DE 698 07 934 T2 ) for transferring such powders or powder coatings in which the powder particles are first charged in the presence of magnetic particles and transferred and applied to the substrate by means of an electric field between a brushing drum and a substrate roll on which the substrate is located, the method of present invention.

object The invention is a method for mixing and gentle Transport and transfer of powders on substrates, the powder particles first in the Special by friction in the presence of magnetic particles be charged, then by means of a fluidized bed and optionally transported one or more mixing rollers and then with Help an electric field between a brushing drum and a substrate roller, on which the substrate is located transferred to the substrate and be applied, characterized in that the mixing and the transport of the powder particles and the magnetic particles be carried out by means of a fluidized bed, wherein the powder continuously deposited on the substrate and simultaneously from Outside newly fed will, while the magnetic particles (carriers) remain in the system.

Fluidized bed processes are known per se to the person skilled in the art. They are based on the following principle:
When gases are passed through from below on fine, air-permeable, fine-grained particles, under certain flow conditions a state is established which is that of a boiling one Fluid resembles; the layer causes bubbles, and the particles are in a continuous, swirling up-and-down motion within the layer, thus remaining in a quasi-floating state. Therefore, one speaks of floating bed, fluidized bed, fluidized bed (in contrast to the fixed bed) or Fluidatbett and fluidizing. The fluidized bed is formed when a certain limit of the speed of the gas flowing through from below is reached. This point, where the quiescent layer merges into a swirling layer and the fixed bed merges into a fluidized bed, is called a loosening point or a vortex point. Essentially, at the fluidizing point, the gravity of the particulates is compensated by the resistance to flow. Achieving this point depends on a number of physical factors such as density, size, distribution and shape of the particles, properties of the fluid and design of the equipment.

The for the production of the fluidized bed required air-permeable Floors are e.g. commercially available under the trade names SINTERPOR or CONIDUR.

The Fluidized bed can be like a liquid through openings flow out transported through pipes be on an inclined surface, e.g. a conveyor trough, drain off, etc.

• a) Rasche Verteilung des Frischpulvers.
• b) Rasche Aufladung infolge hoher Dynamik der Wirbelschicht.
• c) Das Pulver bzw. der Pulverlack kann trotz seiner geringen Dichte direkt in das Fließbett eingetragen werden und wird nicht durch den hohen Druck nach oben geblasen.
• d) Weniger mechanische Belastung auf eventuell noch vorhandene Mischrollen und auf die Bürsttrommel (die Mischung fließt wie eine Flüssigkeit).
• e) Die Walzen zum Fördern fallen (mehrheitlich) weg.
• f) Nach dem Stoppen der Verwirbelung (Fluidisierung) reduziert sich das Volumen der Mischung um ca. 1/3. Damit taucht die Bürsttrommel nicht mehr in die Mischung aus Trägerteilchen/Pulver ein. Beim Wiederanfahren der Anlage kann die Walze (z.B. Bürstwalze) ohne große Kraftaufwendung in Drehung versetzt werden.

This concept makes use of the inventive method. In this case, the abovementioned carrier particles or carriers are mixed with the powder particles in a fluidized bed. This has the following surprising advantages:

• a) Rapid distribution of fresh powder.
• b) rapid charging due to high dynamics of the fluidized bed.
• c) The powder or the powder coating can be registered directly in the fluidized bed despite its low density and is not blown up by the high pressure.
• d) Less mechanical stress on any mixing rollers still present and on the brushing drum (the mixture flows like a liquid).
• e) The rollers for conveying fall (by a majority) away.
• f) After stopping the turbulence (fluidization), the volume of the mixture is reduced by about 1/3. Thus, the brush drum is no longer immersed in the mixture of carrier particles / powder. When restarting the system, the roller (eg brush roller) can be rotated without much effort.

The inventive method continues to be based on the surprising Finding that the brushing drum while the short residence time in the fluidized bed, a number of carrier / powder particles absorbs sufficient to the desired layer thickness on the Substrate, although by the generation of the fluidized bed necessary injection of air into the mixture of powder and carrier particles their density decreases considerably.

The inventive method leads to a longer one Life of the carrier particles. Beyond that on the substrate to be coated more homogeneous layers by uniform distribution of the continuously supplied Powder, especially in the horizontal direction achieved. This is a significant advantage over the method known in the art, in which mixing rollers The powder is used only vertically towards the brushing drum transport.

All in all can the inventive method performed with devices be, which have less mechanically driven parts, so that they also can not block or clog.

By the elimination of the mixing rollers can make the overall system much easier be modified without the mechanics of mixing drums consuming (eg larger tank in combination with larger brush drum Etc.).

The inventive method is preferably used in the production of resin-coated Copper foils for the PCB production. However, it can generally be used for the delivery of Mixtures of powder particles and carrier particles to the brushing roller in electrographic devices be used. In particular, the method according to the invention also for two K toner systems are suitable, i. those where the powder on consumption is dosed.

The in the method according to the invention used powder paint particles generally have a size of <150 microns and preferably <100 microns, most preferably <50 μm.

The carrier particles generally have a size of 10-150 μm and preferably 20-100 μm on.

• (i) Vermischen a) eines polymeren Binders, eines Oxazenharzes, eines Cyanatesters oder eines Maleimids, b) eines Härters oder Initiators, c) eines Lackadditivs, d) gegebenenfalls eines Füllstoffs, e) gegebenenfalls eines kompatibilisierenden Polymers und gegebenenfalls weiterer Komponenten
• (ii) Schmelzextrusion des gemäß Stufe (i) erhaltenen Gemischs und
• (iii) Mahlen und Sieben des extrudierten Gemischs.

Preferably, in the process according to the invention a curable powder coating is used which comprises particles which are obtainable by

• (i) mixing a) a polymeric binder, an oxazene resin, a cyanate ester or a maleimide, b) a hardener or initiator, c) a paint additive, d) optionally a filler, e) optionally a compatibilizing polymer and optionally further components
• (ii) melt extrusion of the mixture obtained according to step (i) and
• (iii) milling and sieving the extruded mixture.

According to one preferred embodiment the powder coating in the uncured state has a glass transition temperature of at least 20 ° C, preferably at least 25 ° C and most preferably of at least 30 ° C and in the cured state a glass transition temperature of at least 150 ° C, preferably at least 160 ° C and most preferably of at least 170 ° C, each measured with DSC.

For further processing of the method according to the invention coated substrate, it is preferred if the degree of cure (measured by DSC) is in the range of 1-70% and preferably 10-50%.

Of Further, the polymeric binder is preferably substantially one solid at room temperature epoxy resin. The glass transition temperature of the resin should preferably be at least 25 ° C be.

Of the Powder paint may also preferably be a mixture of epoxy resins include. This mixture preferably has a glass transition temperature of> 25 ° C not cured State on. Your molecular weight (number average molecular weight) is generally> 600.

suitable Epoxy resins for the preparation of the powder coating are, for example in: Clayton A. May (Ed.) Epoxy Resins: Chemistry and Technology, 2nd Ed., Marcel Dekker Inc., New York, 1988.

preferred Blends of epoxy resins include standard epoxy resins on bisphenol A and bisphenol A diglycidyl ether. The epoxy equivalent weight of these resins is> 300 g / equivalent. Such a resin is, for example, D.E.R. 6508 (available from Dow Chemicals).

at best can also epoxy resins based on bisphenol F and bisphenol S added become.

Of Further, the mixture may comprise multifunctional epoxy resins. The functionality of these resins is> 3. Examples of such multifunctional epoxy resins are Epoxy Cresol Novolac, Epoxyphenol Novolac and naphthol-containing multifunctional epoxy resins.

Examples The above-mentioned epoxy resins are bisphenol A epoxy resins such as D.E.R. 667-20, D.E.R. 663UE, D.E.R. 692H, D.E.R. 692, D.E.R. 662E, D.E.R. 6508, OF THE. 642U-20 (available from Dow Chemicals), epoxy cresol novolacs such as Araldite ECN 1299, Araldite ECN 1280 (Vantico), EOCN-103 S, EOCN-104, NC-3000, EPPN 201, EPPN-502 H (Nippon Kayaku), naphthol epoxy resins such as NC 7000-L (Nippon Kayaku), and brominated epoxy resins, such as Araldite 8010 (Vantico), BREN-S (Nippon Kayaku), ESB-400T (Sumitomo) and Epikote 5051 (Resolution). In addition you can also modified epoxy resins are used. Such modifications For example, the use of chain breakers for regulation molecular weight, so-called "high-flow" resins, and the use of multifunctional Monomers for producing branched resins.

One Particularly preferred powder coating comprises as component a) approximately 50-90% by weight of epoxide and about 5-20 Wt .-% cyanate ester, as component b) about 0.5-5 wt .-% dicyandiamide and about 0.1-2 % By weight of 2-phenylimidazole, for example about 85% by weight of epoxide, 10 Wt .-% cyanate ester, about 2 wt .-% dicyandiamide as a hardener and about 1% by weight of 2-phenylimidazole as initiator.

As already mentioned, in addition to the epoxy resins, polymeric binders may also be cyanate esters be. These can be used in the preparation of the powder coating both in monomeric form as well as in the form of oligomers or prepolymers.

suitable Cyanate esters are bifunctional cyanate esters, such as BADCy, Primaset Fluorocy, Primaset MethylCy, or multifunctional cyanate esters, such as Primaset BA-200, Primaset PT 60, Primaset CT 90, Primaset PT 30. All the aforementioned bifunctional and multifunctional cyanate ester are available from Lonza, Basel, Switzerland.

Especially preferred cyanate esters are BADCy and its prepolymers (e.g., Primaset BA-200).

Next The cyanate esters, the component a) also 1-oxa-3-aza-tetralinhaltige Compounds (oxazene resins). These are used in the production the powder coating first also used in monomeric form.

Preferred oxazene resins are those obtained either by reacting bisphenol-A with aniline and formaldehyde or by reacting 4,4'-diaminodiphenylmethane with phenol and formaldehyde. Further examples can be found in WO 02/072655 A1 and EP 0 493 310 A1 and WO 02/055603 A1 and in Macromolecular Chemistry, Macromolecular Symposia (1993), 74 (4th Meeting on Fire Retardant Polymers, 1992), 165-71, EP 0 493 310 A1 . EP 0 458 740 A1 . EP 0 458 739 A2 . EP 0 356 379 A1 and EP 0 178 414 A1 ,

Finally are also used for the preparation of the powder paint maleimides the Skilled in the art and, for example, in Shiow-Ching Lin, Eli M. Pearce, High-Performance Thermosets, Carl Hanser Verlag, Munich 1994, chapter 2.

Component b) of the aforementioned resin composition comprises a hardener or initiator. Such curing agents and initiators are known per se to the person skilled in the art and include latent curing agents having low activity at room temperature, such as phenolic hardeners such as DEH 90, DEH 87, DEH 85, DEH 84, DEH 82 (available from Dow Chemicals, US), dicyandiamide or Derivatives thereof, such as Dyhard OTB, Dyhard UR 200, Dyhard UR 300, Dyhard UR 500, Dygard 100, Dyhard 100S, Dyhard 100 SF and Dyhard 100 SH (available from Degussa, Germany), bisphenol A, acid anhydrides, such as phthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, chlorendic anhydride, dodecenylsuccinic anhydride, bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid anhydride, aromatic and aliphatic amines such as diaminodiphenyl sulfone, diaminodiphenyl ether, diaminodiphenylmethane or ring-substituted dianilines such as Lonzacure ^® M-DEA, Lonzacure M-DIPA ^{®, ®} Lonzacure M-MIPA, Lonzacure ^® DETDA 80 (all of the above compounds are available from Lonza, Basel, Switzerland).

Preferably dicyandiamide or modified dicyandiamide is used.

In the resin composition, the hardeners or initiators in a Amount below 10% by weight, preferably below 5% by weight, used (lower limit: about 0.1 wt .-%).

preferred Initiators are imidazoles and derivatives thereof, such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, Bis (2-ethyl-4-methylimidazole), 2-undecylimidazole, 2,4-diamino-6 (2'-methyl-imidazole (1 ')) ethyl-s-triazine and 1-cyanoethyl-2-undecylimidazole. In addition, the salts can be formed from Imidazoles and carboxylic acids be used. Other initiators are 1,8-diazabicyclo (5.4.0) undecene (DBU) and the boron trihalide-amine complexes, e.g. BF3-amine. Further examples can be found in Clayton A. May (Ed.) Epoxy Resins: Chemistry and Technology, 2nd ed., Marcel Dekker Inc., New York, 1988.

The Resin composition further comprises as component c) paint additives. These include leveling agents, degassing aids and lubricants Understood. These are known per se to the person skilled in the art. Typical examples are butyl acrylate polymers as flow control agents, benzoin as Degassing aids and waxes as a lubricant. Furthermore, as Paint additives for example stabilizers can be used.

The Paint additives are present in the resin composition in an amount of generally 0.1-10% by weight, preferably 0.2-5 Wt .-% included.

Under Paint additives are also understood as so-called "adhesion promoters". These are for the adhesion to the copper substrate makes sense.

Of the Powder paint can also contain organic and inorganic fillers d).

These fillers are expediently in an amount of 5% by weight to 300% by weight, preferably 10 to 200 Wt .-%, most preferably 10 wt .-% to 100 wt .-% in the Powder paint used. These quantities refer to the Sum of components a), b) and c) of the powder coating.

Examples for organic fillers are fluorine-containing polymers such as polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene Copolymer (FEP), tetrafluoroethylene / ethylene copolymer (E / TFE), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride terpolymer (THV), polytrifluorochloroethylene (PCTFE), trifluorochloroethylene / ethylene copolymer (E / CTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoroalkoxy copolymer (PFA), Tetrafluoroethylene / perfluoro-methyl vinyl ether copolymer (MFA), also polyvinyl chloride (PVC), polyphenyl ether (PPO), polysulfone (PSU), polyarylethersulfone (PES), polyphenyl ether sulfone (PPSU), polyphenylene sulfide (PPS), polyether ketones (PEK) and polyetherimide (PEI).

Especially preferred organic fillers are tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE) and polyphenyl ether (PPO).

In the powder paint can as organic fillers especially those that are not used during processing melt. Alternatively you can such organic fillers are used, the melting and on cooling a phase separation demonstrate.

Next the organic fillers can in the powder coating and inorganic fillers are used.

Such fillers are, for example, quartz glass, such as Silbond 800 EST, Silbond 800 AST, Silbond 800 TST, Silbond 800 VST, Silbond 600 EST, Silbond 600 AST, Silbond 600 TST, Silbond 600 VST (available from Quarzwerke Frechen, Germany), fumed silica such as Aerosil 300 and Aerosil R 972, precipitated Silica such as Ultrasil 360, Sipernat D 10, Sipernat 320 (available from Degussa, Germany), calcined kaolin, such as Polestar (Imerys, St Austell, UK), Santintone (Engelhard Corporation, Iselin, NJ, US), alumina, magnesia, zirconia, aluminum silicates, Calcium carbonate and barium sulfate, with quartz glass and kaolin as fillers are preferred. Also to be mentioned are ceramics, v. A. also such with low or negative expansion coefficient.

The advantages of the powder paint are that it is possible to choose the one that best meets the challenges presented to optimize the product properties of a variety of fillers. For example, a once-selected epoxy resin mixture can be modified and adjusted as needed. Even difficult to process fillers can be incorporated easily. Thus, electrical properties, such as dielectric constant (D _k ), dielectric loss factor (tan δ), breakdown resistance, surface resistance, volume resistance and mechanical properties, such as flexural strength, impact resistance, tensile strength, and other material properties such as thermal expansion coefficient (CTE), flammability, etc. in customize the way you want. The filler need not be soluble or stably dispersible in organic solvents. As a consequence, materials can be used as fillers that previously could not be used in the SBU (Sequential Buildup) range or only to a limited extent, such as the organic fillers already mentioned.

By the fillers can the electrical and mechanical properties of the powder coating or the varnish layer produced therefrom influenced or adjusted become.

So can for example fillers with low dielectric constant, such as PTFE, FEP and kaolin, can be used to appropriate To produce paint layers with low dielectric constant.

In analogous way can control other electrical properties.

Under the mechanical properties that are influenced by the fillers can, In particular, properties such as the thermal expansion coefficient, the impact resistance and the tensile strength understood.

to Influencing the thermal expansion coefficient are the following fillers particularly suitable: quartz glass, kaolin, calcium carbonate and ceramics with a negative coefficient of expansion.

The Bending strength is influenced or adjusted by PPO, for example.

According to one preferred embodiment the invention has the cured Powder coating a coefficient of thermal expansion (CTE) of <70 ppm / ° C and preferably <60 ppm / ° C in x-, y and z direction.

According to one another preferred embodiment is the dielectric constant of the paint in the cured Condition <3.8, preferably <3.6. Furthermore, glass transition temperatures the cured one Formulation of over 150 ° C, preferably above 160 ° C, preferably.

Finally, flame retardant materials can also be used as fillers. Examples of these are inorganic materials which release water on heating, such as aluminum hydroxide, available for example as Martinal OL-104, Martinal OL-111 (Martinswerk GmbH, Bergheim, Germany) or Apyral 60 D (Nabaltec, Schwandorf, Germany), magnesium hydroxide for example as magnesium hydroxide 8814 (Martinswerk GmbH, Bergheim, Germany) or Mg-Hydroxide SIM 2.2 (Scheruhn Industrie-Minerals, Hof, Germany), phosphorus-containing organic compounds, such as triphenyl phosphate (TPP), tricresyl phosphate (TCP), cresyl diphenyl phosphate (CDP), tertiary phosphine oxides, such as Cyagard ^® and Reoflam ^® 410, red phosphorus in form of a dispersion in an epoxy resin, such as Exolit RP 650, or in the form of a powder, such as Exolit OP 930 (both products are available from Clariant GmbH, Frankfurt, Germany and antimony trioxide.

Of Furthermore, the flammability of the powder coating can also by the Component c), i. the paint additives, influenced and adjusted become. In this context, for example, phosphorus-containing and to mention nitrogen-containing flame retardants.

Of the Powder coating may further optionally compatibilizing polymers contain. Such compatibilizing polymers are, for example Di- or triblock copolymers such as styrene-butadiene-styrene or styrene-butadiene-methyl methacrylate block copolymers (Atofina, France).

Of Furthermore, the powder coating usual Additives and additives that are used in the processing of Epoxy resins usually can be used.

at the preparation of the powder coating become the components described above a), b), c) and optionally d) and e) first dry to a powder ground.

there It may be possible be expedient pre-mix and extrude individual components, to make a masterbatch.

This The procedure must be used in particular if certain Components are difficult to incorporate. These are then merged in advance incorporated, such "masterbatches" are also commercially available The resins, for example, it is conceivable, two resins in advance with each other to mix - one such a procedure is used in particular if one the resins have a low glass transition temperature having. Furthermore, this method can be used when certain components are used only in small quantities.

The The aforementioned components or "masterbatches" are premixed dry and ground. Before grinding, the mixture is optionally cooled.

To intimate mixing (and possibly cooling) dry the material dry to obtain a powder and Powder afterwards extruded. This extrusion ensures complete homogenization of the components and represents a key step of the overall process represents.

To The extrusion is dry milled the material and the oversize grain separated, expediently a sieve size in the range of less than 10 μm up to 500 μm and preferably below 100 μm, which ensures a corresponding particle size is used. Particularly suitable for grinding are classifying mills, such as e.g. Hosekawa MicroPul.

The already mentioned melt extrusion is preferably carried out so that the conversion of the reactive component is less than 20%, preferably less than 10%. This reaction is due to the formation of a melt during extrusion. The degree of conversion can be determined by the person skilled in the art by Thermoana be determined. The corresponding extrusion parameters (to achieve such a degree of conversion) can be determined by the skilled person by simple experiments. They depend on the type of extruder and the type and amount of components used. For example, as a extruder, a Buss co-kneader can be used, in which the aforementioned components are extruded. Subsequently, as already mentioned, the mass is cooled and comminuted. The finished powder coating mixtures preferably have an average particle size in the range from 1 .mu.m to 500 .mu.m, in particular from 10 .mu.m to 100 .mu.m.

Next The powder coating particles thus prepared can in the process according to the invention other powder coatings may also be used, e.g. in Pieter Gillis de Lange, Powder Coatings Chemistry and Technology, 2nd edition, Vincentz Network, Hannover 2004 are described.

at the method according to the invention can also both organic and inorganic powders as coating medium be used, which are not melted itself readily, but at higher Temperature can be sintered. For example, you can glasses coated with the method according to the invention which are either self-conducting or a conductive coating (such as ITO (indium tin oxide) glass), e.g. with titanium oxide nanoparticles, such as they are described for example under www.nanophase.com. These Coating can then be subsequently sintered at a higher temperature (400-600 ° C) become. Thus, the inventive method for the rational Production of solar cells are applied to dye-based (See M. Graetzel, Nature, 353 (24), 737, 1991).

With the method according to the invention can especially smooth surfaces to be obtained. One parameter for this is the so-called gloss level, which can be determined with a glossmeter. Drive with the Ver invention obtained surfaces generally have a gloss level <60, preferably <30 and particularly preferably <20 (measured with a glossmeter from Byk Gardner at 60 °).

The Invention is illustrated by the following examples and comparative examples explained in more detail.

example 1

Production of the powder coating:

380 Parts of an epoxy resin (mp 90-110 ° C, epoxy equivalent weight 400 g / eq), 116 Parts of a solid epoxy resin (4.3-4.9 eq / kg), 160 parts filler (Particle diameter <8 μm), 25 parts Dicyandiandiamide (particle diameter <6 μm), 16 parts each of benzoin and methylimidazole and 12 parts of a flow control agent (Acrylic polymer) and 3 parts of additives for increasing adhesive strength mixed in a premixer and then extruded (twin-screw extruder the company OMC, Saronno, Italy, type EBVP 20/24; Temperature 100 ° C, torque 65%). The subsequent Grinding takes place in a mill the company Fritsch (Pulverisette 14, 15000 U / min). The oversize is separated by sieving (<100 μm). 50% of the particles have a particle size <30 microns on.

Application via EMB in combination with fluidized bed:

24 kg carrier particles consisting of a magnetic core (magnetite), which with a Layer of silicone polymer is surrounded with 4 kg of powder paint mixed and introduced into the EMB unit. By applying a pressure of 6 bar becomes the carrier particle / powder Fluidized mixture. The speed of the brushing drum is 35% of the set to maximum speed, which is sufficient to cover evenly to ensure. On the substrate drum is a 12 micron thick copper foil (width 620 mm), which moves at a speed of 3 m / min. Fresh powder is fed continuously from the outside (190 g / min). After donning a positive voltage on the brush drum jump the powder particles on the copper over. In a downstream melting unit, the powder is melted and partially cured (35% by DSC). The film thus obtained has a gloss level <10 on (measured with a Glossmeter Byk Gardner at 60 °).

Comparative Example 1

used was the powder coating of Example 1. The coating takes place in the way that instead of the fluidized bed an arrangement of mixing rollers the mixing of carrier particles and powder particles and their transport to the brushing drum takes over. The other parameters are identical.

The table shows the layer thicknesses on a 62 cm wide copper foil after 8.5 m coating at five different positions:

1

brush drum

2

substrate drum

3

mixing drums

4

sheet to return the Carrier

5

contraption for adjusting the height the brush

6

Role, from which the substrate is unrolled

7

heating source

8th

role for winding up the coated substrate

9

Container

Claims (13)

Process for mixing and gentle Transport and transfer of powders on substrates, wherein the powder particles by Friction in the presence of magnetic particles are charged then by means of a fluidized bed and optionally one or more mixing rollers transported and subsequently by means of an electric field between a brushing drum and a substrate roll on which the substrate is located, transferred to the substrate and be applied, characterized in that the mixing and the transport of the powder particles and the magnetic particles be carried out by means of a fluidized bed, wherein the powder continuously deposited on the substrate and at the same time of ANSSEN fed will, while the magnetic particles (carriers) remain in the system. Method according to claim 1, characterized in that that the substrate is a metal foil or metallized plastic film, a conductive plastic film, conductive or by a coating conductive glass is. Method according to claim 2, characterized in that the substrate is ITO (indium tin oxide) glass. Method according to claim 1, characterized in that that the substrate is a metal foil, which is in intimate contact with a fiber-reinforced woven material or fleece is located. Method according to claim 4, characterized in that that the fiber reinforced Material is selected from fiberglass fabrics and high performance fibers. Method according to claim 5, characterized in that that the high-performance fibers aramid fibers, carbon fibers or ceramic fibers are. A method according to claim 1, characterized in that as powder paint particles obtainable by (i) mixing a) a polymeric binder, an oxazene resin, a cyanate ester or a maleimide, b) a hardener or initiator, c) a paint additive, d) optionally a filler, e) optionally a compatibilizing polymer and optionally further components (ii) melt extrusion of the mixture obtained according to step (i) and (iii) grinding and sieving of the extruded mixture. Method according to claim 7, characterized the powder coating particles have a size of <100 μm. Method according to claim, characterized the powder coating particles have a size of <50 μm. Method according to claim 1, characterized in that that the magnetic particles have a size of 20-100 microns. Method according to claim 1, characterized in that that the powder coating applied with a coating thickness distribution of ± 15% is, preferably ± 10%, most preferably ± 5%. Use of the method according to claim 1 prepared coated substrate for the production of printed circuit boards and solar cells. Method according to claim 1, characterized in that the coated substrate has a gloss level <60, measured with a glossmeter from Byk Gardner at 60 °.